The power output of a wind turbine and the loads exerted on the wind turbine by the wind are to a large extent dependent on the orientation of the wind turbine with respect to the wind. Therefore means are available on most wind turbines to adjust the orientation of the wind turbine such that the optimum orientation can be achieved. In addition, means are available on most wind turbines which allow the wind turbine to be adjusted, by for example changing the angle of attack of the blades dependent on the wind speed.
In order for the wind turbine to be optimally adjusted, the wind speed and direction need to be known. By adjusting the wind turbine more optimally, the power output of the wind turbine will be increased and the loads on the wind turbine will be decreased.
In addition, accurate measurement of the wind speed and direction allows the power performance of the wind turbine to be determined accurately. Accurate power performance data for a wind turbine is very important for proper adjustment and monitoring of wind turbines.